Activated carbons are widely used as adsorbents, for example, to remove impurities or adjust the concentration of dissolved components. Further, due to their high specific surface area, activated carbons are also used as supports, etc., for various metals and organic substances.
Among such activated carbons, wood-based steam-activated carbons are particularly widely used in the food industry and chemical industry (in particular, pharmaceutical production), and in the purification process of water treatment, etc., because micropores and mesopores are present therein with well-balanced distribution, the impurity content is low, and there is no risk of solution pollution. Wood-based steam-activated carbons are also suitably used as catalyst supports because they have a high specific surface area, have mesopores where the substrate reaction occurs, and have a low impurity content.
Thus, wood-based steam-activated carbons are industrially useful materials; however, the use of wood powder as their raw material causes a limitation in that only powdered activated carbons can be obtained. When powdered activated carbons are used, dust generation may be problematic. Further, it was necessary, after use, to separate the activated carbon and the solution by filtration, which obstructed the use of powdered activated carbons.
Lumber can also be used as the raw material in place of wood powder, and carbonized to form charcoal, followed by steam activation; however, the resulting activated carbons are light and flexible, and cannot be used as granular activated carbons.
Moreover, the raw material wood powder is produced in the process of lumber sawing; however, the yield is decreasing because of lumber resource conservation. Furthermore, methods for effective utilization of wood powder for applications other than activated carbons have progressed; therefore, it is becoming difficult to use wood powder as the raw material for activated carbons.
The development of granular activated carbons that have high pore distribution and purity equivalent to those of wood-based steam-activated carbons is thus anticipated, even without using a wood powder raw material.
As a method for manufacturing an activated carbon having many mesopores, PTL 1 discloses an activated carbon for highly treating clean water obtained by mixing 100 parts by weight of carbonaceous raw material with 0.2 to 1.5 parts by weight (in terms of calcium) of at least one calcium compound, and carbonizing and activating the mixture; and also discloses a method for manufacturing the same.